@@ -8,14 +8,12 @@ import (

 type Args map[string][]string

-/*

-Parse the argument to the filter flag. Like

-

-  `docker ps -f 'created=today' -f 'image.name=ubuntu*'`

-

-If prev map is provided, then it is appended to, and returned. By default a new

-map is created.

-*/

+// Parse the argument to the filter flag. Like

+//

+//   `docker ps -f 'created=today' -f 'image.name=ubuntu*'`

+//

+// If prev map is provided, then it is appended to, and returned. By default a new

+// map is created.

 func ParseFlag(arg string, prev Args) (Args, error) {

 	var filters Args = prev

 	if prev == nil {

@@ -37,10 +35,13 @@ func ParseFlag(arg string, prev Args) (Args, error) {

 var ErrorBadFormat = errors.New("bad format of filter (expected name=value)")

-/*

-packs the Args into an string for easy transport from client to server

-*/

+// packs the Args into an string for easy transport from client to server

 func ToParam(a Args) (string, error) {

+	// this way we don't URL encode {}, just empty space

+	if len(a) == 0 {

+		return "", nil

+	}

+

 	buf, err := json.Marshal(a)

 	if err != nil {

 		return "", err

@@ -48,11 +49,12 @@ func ToParam(a Args) (string, error) {

 	return string(buf), nil

 }

-/*

-unpacks the filter Args

-*/

+// unpacks the filter Args

 func FromParam(p string) (Args, error) {

 	args := Args{}

+	if len(p) == 0 {

+		return args, nil

+	}

 	err := json.Unmarshal([]byte(p), &args)

 	if err != nil {

 		return nil, err

@@ -61,3 +61,18 @@ func TestParam(t *testing.T) {

 		}

 	}

 }

+

+func TestEmpty(t *testing.T) {

+	a := Args{}

+	v, err := ToParam(a)

+	if err != nil {

+		t.Errorf("failed to marshal the filters: %s", err)

+	}

+	v1, err := FromParam(v)

+	if err != nil {

+		t.Errorf("%s", err)

+	}

+	if len(a) != len(v1) {

+		t.Errorf("these should both be empty sets")

+	}

+}